1. Field of the Invention
The present invention relates to a method of and an apparatus for peeling chips fabricated on a wafer of silicon or the like off a sheet attached to the reverse side of the wafer in a process of manufacturing ICs or the like.
2. Description of the Related Art
FIG. 10 of the accompanying drawings shows a conventional chip peeling apparatus 10. As shown in FIG. 10, the conventional chip peeling apparatus 10 includes a base 12 having a hole 16 defined therein which is connected to a first vacuum source (not shown). A tubular member 18 has an end fitted in an upper open end of the hole 16 and a flange 20 projecting radially outwardly from an outer circumferential surface thereof. The flange 20 is fixedly mounted on the end of the base 12 which defines the upper open end of the hole 16, thereby supporting the tubular member 18 on the base 12. A cylindrical member 22 is inserted in the hole 16 and has an outer wall surface and a distal end spaced from an inner wall surface of the tubular member 18 which defines a hole 24 therein. A pin 26 is inserted in the cylindrical member 22 for axial sliding movement in the cylindrical member 22, and supports a plurality of needles 28 mounted upwardly on a distal end of of the tubular member 18 and fixed to the tubular member 18 by a cover 32. The suction nozzle 30 has a plurality of holes 34 defined therein for insertion of the needles 28.
A seat 36 is positioned in upwardly spaced relation to the base 12, and the suction nozzle 30 has a distal end projecting upwardly slightly from a hole 37 that is defined in the seat 36. A suction head 38 is disposed upwardly of the suction nozzle 30 for movement toward and away from the suction nozzle 30. The suction head 38 has an axial hole 40 defined therein which is connected to a section vacuum source (not shown).
A process of peeling chips 42 such as of ICs or the like fabricated on a wafer off a sheet 44 using the chip peeling apparatus 10 will be described below.
As shown in FIG. 10, when the sheet 44 to which the chips 42 are attached is moved to a position above the seat 36 and brought into held against an upper portion of the suction nozzle 30, the sheet 44 is curved upwardly. When the center of a desired one of the chips 42 is aligned with the center of the suction nozzle 30, the first vacuum source (not shown) is actuated to attract the sheet 44 to the suction nozzle 30.
Then, the pin 26 is lifted to cause the needles 28 to pierce and project through the sheet 44, and ascend with the chip 42 placed on the tips of the needles 28, as shown in FIG. 11 of the accompanying drawings. At this time, since the sheet 44 is attracted to the suction nozzle 30, the chip 42 is peeled off the sheet 44.
Thereafter, the suction head 38 is moved toward the suction nozzle 30 and brought into abutment against the chip 42. The second vacuum source (not shown) is actuated to attract the chip 42 off the sheet 44 to the suction head 38. The chip 42 will then be transferred to another location.
FIG. 12 of the accompanying drawings shows another conventional chip peeling apparatus 50. As shown in FIG. 12, the conventional chip peeling apparatus 50 includes a peeling base 52 having a plurality of protrusions 54 with flat tops, the protrusions 54 having heaters (not shown). The peeling base 52 has grooves 56 each defined between adjacent ones of the protrusions 54 and communicating with a hole 58 defined in the peeling base 52 which is connected to a vacuum source (not shown). A suction head (not shown) is positioned above one of the grooves 56 for movement toward and away from the peeling base 52.
A sheet 44 with a plurality of chips 42 and streets 59 remaining as cut fragments in gaps between the chips 42 is moved toward a position above the peeling base 52 with the chips 42 above the grooves 56. The protrusions 54 have been heated by the heater to apply heat to the sheet 44, thereby making the sheet 44 stretchable. The vacuum source is actuated to evacuate the grooves 56, whereupon the sheet 44 is stretched and curved in the direction in which the vacuum is developed, as indicated by the two-dot-and-dash lines. At this time, the chips 42 have their peripheral edges supported on the flat tops of the protrusions 54, and the sheet 44 is peeled off central regions of the chips 42.
Then, the suction head (not shown) is moved toward a desired one of the chips 42. Because of an attracting action of the suction head, the sheet 44 is peeled off the peripheral edges of the chip 42, which is attracted to and held by the suction head. The chip 42 will then be transferred to another location.
The former chip peeling apparatus 10 is disadvantageous in that the tips of the needles 28 tend to damage the surface of the chip 42. When the needles 28 are elevated, the sheet 44 itself may also be stretched and lifted. At this time, the needles 28 may not pierce the sheet 44, and hence may not form holes in the sheet 44, with the result that the chip 44 may not be separated from the sheet 44.
The latter chip peeling apparatus 50 is also problematic in that when the sheet 44 is attracted, the chip 42 itself may be curved, and when the sheet 44 is peeled off, the chip 42 may jump off, resulting in a positional deviation which may prevent the suction head from attracting the chip 42. As a result, when the chip 42 is to be transferred to and placed in a further process, the chip 42 cannot be positioned with accuracy. When the chip 42 is curved, it cannot be prevented from being unduly curved to an unnecessary extent, and hence may be cracked or broken. If the chip 42 is broken, it is liable to damage the sheet 44, eliminating the vacuum thereby to fail to peel other normal chips 42 off the sheet 44. Furthermore, when a chip 42 is to be peeled off by the suction head, a street 59 which lies at the same height as the chip 42 may also be peeled off the sheet 44, and attracted and transferred together with the chip 42 by the suction head.